Imaging apparatuses described above include one that has a zoom lens barrel having a zoom function which changes an imaging magnification by moving plural lens units (including a lens and its holding member) in an optical axis direction (see Japanese Patent Laid-Open No. 2001-324663).
In the zoom lens barrel disclosed in Japanese Patent Laid-Open No. 2001-324663, a plurality of lens units are moved in the optical axis direction by cams formed on a cam tube which can rotate around the optical axis. Here, a plurality of lens units are prevented from rotating so as not to rotate around the optical axis together with the cam tube. In other words, a plurality of lens units are driven in the optical axis direction by rotations of the cam tube while being guided in the optical axis direction.
Imaging apparatuses are desired to have a higher magnification ratio, but on the other hand they are required to be smaller and in particular thinner so that they can be easily carried around. A multistage stretching structure that shortens the size in the optical axis direction of each tubing member in the zoom lens barrel is conceivable for both the high magnification ratio and the low profile. However, the multistage stretching structure makes it difficult to arrange the cams for driving a plurality of lens units without interfering with each other.
Japanese Patent No. 3,842,087 discloses a zoom lens barrel provided with a first and a second cam for moving first and second lens units in the optical axis direction respectively on an outer circumferential surface and an inner circumferential surface of a rotation tube so that the first and second cams are provided without interfering (intersecting) with each other.
In the zoom lens barrel disclosed in Japanese Patent No. 3842087, the first lens unit and the second lens unit are respectively guided in the optical axis direction by separate tubing members (first and second linearly moving tubes). Therefore, relative decentering between the first and second linearly moving tubes is highly likely to cause similar decentering between the first and second lens units, too. In particular, since lens sensitivity has become high due to size reduction of the zoom lens barrel, even a slight decentering can largely influence the optical characteristics.